Github link on the API page's sidebar

[leobalter]

This is based on the results from the google analytics and heatmaps analysis.

There're some considerable clicks on the github icon on the very bottom of the API page.

We should add a Github and Contributing links to the API pages' sidebar.

[leobalter]

I'm thinking about not inserting the Contributing page yet, that would require some hacks on the Docs and parsers.

Probably better than this is adding the entire contributing section to the API page's sidebar.

[Krinkle]

For future reference:

• API pages: https://gruntjs.com/api/grunt
• Other pages for comparison: https://gruntjs.com/getting-started - these have a "Community" sidebar section already, which includes the Contributing link.